1. Field of the Invention
The present invention generally relates to a system for rewriting information in a rewritable memory provided in a portable remote terminal, such as a portable telephone, and to a portable remote terminal applicable to the system, and more particularly to a system in which a program in a rewritable memory can be rewritten under a condition in which the rewritable memory is mounted in the portable remote terminal.
Portable telephones, which are one type of portable remote terminal, have been spread in some years ahead, and have been greatly miniaturized. Due to miniaturization of parts of the portable telephone and to a technique by which many parts are mounted in a narrow area, the miniaturization of the portable telephone has been achieved. The portable telephone is controlled by a CPU (a micro computer) carrying out processes in accordance with programs stored in a program memory. In a case where functions of the portable telephone are to be changed, the programs in the program memory must be rewritten.
2. Description of the Related Art
In a portable telephone, a ROM device (Read Only Memory Integrated Circuit) is used as a program memory in which programs are to be stored. The following ROM devices are mounted in the portable telephone; an EPROM (Erasable and Programable ROM), a ROM which is programmable only once (so called a one-time ROM), a mask ROM which is programmable by wiring in the IC, and the like. These ROM devices are mounted on sockets fixed on printed circuit boards.
A ROM device is removed from a socket, and a program stored in the ROM device is then rewritten. In a case of a ROM device in which a program is not rewritable, such as a one-time ROM or a mask ROM, the ROM device is replaced by a new one in which an updated program has been stored. In a case of an EPROM, a ROM eraser erases a program in the EPROM using ultraviolet radiation, and a ROM writer electrically writes a new program in the EPROM.
A space required for mounting the conventional program memory on-a printed circuit board with a socket is greater than that required for directly mounting the program memory on a printed circuit board without a socket. That is, miniaturization of the personal telephone is hampered by the socket on which the program memory is to be mounted. The program stored in the program memory may be rewritten after the portable telephone has been manufactured. Thus, if the program memory is directly soldered on the printed circuit board without a socket, the program memory soldered on the printed circuit board must be removed therefrom in order to rewrite the program in the program memory. In this case, it is not easy to remove the program memory from the printed circuit board.